Manufacturers and suppliers of drugs and other valuable substances packaged in glass containers, e.g. syringes, have a need to track and trace these containers through their manufacture and their eventual supply to end users, and to ensure that these containers are not counterfeited or faked. This problem is in fact not only applicable to glass, but also to containers made of other materials such as plastics. These needs arise because the manufacturers and suppliers must ensure the following.                The genuine and correct contents arrive at the correct locations.        Product containers can be traced back through the supply process stages for verification or troubleshooting.        Product containers cannot be counterfeited, which would result in the wrong substance being delivered to a customer.        The wrong genuine article cannot end up in the wrong location or with the wrong person.        Customers have complete confidence that none of these above-stated problems has occurred, because there is a secure system in place.        
To achieve an accurate track and trace system requires indelible marking of the product containers. Methods must be available to reliably apply and read the markings at the required locations and by the required people. To secure against counterfeiting requires that the marks should be encoded and decoded in a controlled manner, in such a way that they can be readily verified as genuine and correct.
In many situations the glass product containers are packed into an even larger container, such as a box or carton. For these situations, it is desirable that each of the glass-packaged products should be individually identifiable, such that the correct items are known to be in the correct box at specified stages in the production process and in the supply chain.
Methods of marking glass products for security purposes include printing methods and laser marking methods on the surface of the material. Usually these processes use a code for track and trace purposes.
Ink-jet printing technology is one process for coding products for track and trace purposes. This has been applied in the pharmaceutical industry on various substrates including glass, to create numerical codes and bar codes. (ref Marking & Coding Solutions for Pharmaceutical Applications, Videojet Technologies Incorporated, https://my.videojet.com/videojet/distributors/documents/support/Brochures/v-pharma-flyer.pdf)
A long-wave CO2 laser with scanning optics has been used to engrave a translucent data matrix code onto the surface of glass syringe barrels. The code is 2×2 mm in size comprising a 14×14 data matrix. It is optically read using a camera with back-lighting, and read as a black & white code by image processing software. (ref Pharm. Ind. 71, No. 10, 1770-1774 (2009) and Pharm. Ind. 71, No. 11, 1945-1948 (2009); ECV Editio Cantor Verlag, Aulendorf, Germany). Data matrix codes of 1×1 mm size have also been laser etched onto the finger rest of the syringe. (ref: http://www.gerresheimer.com/en/products-services/news/event-news/eventnewssingle0/article/laser-encoding-gives-syringes-and-vials-an-indelible-id.html)
In another application, green lasers have been used to mark anti-fake labels below the surface of glass bottles for security purposes. (ref Wuhan Lead Laser Co, China http://leadlaser4.en.made-in-china.com/product/RMpEgoOFCikU/China-Green-Laser-Subsurface-Engraving-Flying-Surface-Marking-Machine-LD-EG-F3005-.html).
U.S. Patent Publication No. 2010/0119808 teaches that changes to the refractive index inside glass have been achieved using radiation having a wavelength of up to 400 nm to form subsurface marks up to 50 μm in size. No microcracks are created in the glass and no surface marking occurs. The subsurface marks can be created in a range of 20 to 200 microns below the outer surface of the glass. This '808 publication is expressly incorporated by reference herein, in its entirety.
Remelted glass zones can be created inside bulk glass using a pico-second laser. These zones result in a local refractive index change. (Ref Evaluation Of Non-Linear Absorbtivity In Internal Modification Of Bulk Glasses By Ultra-Short Laser Pulses, by Isamo Miyamoto, Christian Cvecek, Michael Schmidt, Optics Express, 23 May 2011/Vol. 19, No. 11, which is expressly incorporated by reference herein, in its entirety.)
U.S. Pat. Nos. 6,573,026 and 6,853,785 teach that patterns can be created in bulk glass substrates by using a femtosecond laser to modify the refractive index. The pulsed laser beam is translated along a scan path to change the refractive index without resulting in any laser induced physical damage of the material. Each of these '026 and '785 patents is expressly incorporated by reference herein, in its entirety. Also, International Patent Publication No. WO2007/033445 teaches the use of a femtosecond laser to mark codes inside the glass wall of a syringe, to track the products. This '445 publication is also incorporated by reference herein, in its entirety.
A number of optical detection devices useful for analyzing three dimensional structures are known. White light interferometers represent one example of the current state of the art, but they are rather slow. Optical coherence tomography (OCT) is another known technique for measuring a three dimensional pattern, even if the pattern is located at an interface below the surface of an article. OCT is sensitive to changes of index of refraction, surface/interface topologies and absorption. U.S. Pat. No. 6,469,489 describes an array sensor used for parallel optical low coherence tomography which enables real time 3D imaging for topographic and tomographic structures. It provides fast, three dimensional and structural information with spatial resolution in the micrometer range. In depth OCT can achieve resolutions between 10-100 nm for high quality surfaces. For rough surfaces, or strongly scattering systems, the depth resolution is usually between 1-10 micrometers. A plurality of electrical detection circuits with parallel outputs can form a one-dimensional or two-dimensional array sensor for the coherent or heterodyne analog detection of intensity modulated optical signals simultaneously for all pixels with a high dynamic range. The array sensor may be used for optical 3D measurements, and especially in optical low-coherence tomography. OCT is known for investigating the human skin, to control the quality of fast production processes, in SMD pick and place systems, as well as in mechanical inspection systems. Instead of using a time-modulated interferometric signal, frequency domain OCT uses a broad band light source and advanced Fourier analysis to provide very fast and accurate 3D images of objects, such as the human retina. Although fast, frequency domain OCT suffers from a limited depth range. Variants of these detection techniques do not use interferometry, but time-modulated optical signals to measure the distance to an object accurately. The '489 patent is expressly incorporated by reference herein, in its entirety.
At present, all known solutions for marking and measuring glass product containers, i.e. bottles, vials and/or syringes, are controlled by normal 2D cameras with strong illumination to make the markings visible to the camera. This is done because of the high production speeds required in production, which lies between 60-600 pieces per minute. It is currently nearly impossible to measure 3D patterns at such speeds and the usual solutions are therefore limited to 2D patterns and 2D inspection. However, these inspections suffer from several severe drawbacks, as identified below.                1. Inaccuracy of depth of code, as the depth is not measured.        2. Low production yield because of light reflected from surfaces which sometimes makes reading of the codes with normal cameras very difficult.        3. In printed systems and surface engraving, which give good image contrast, there is the danger of particle contamination.        